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I Podreka

Publications and source records attributed to I Podreka.

At least 55 records · Page 3Linked to original sources
PubMed1991

Contributions of occipital and temporal brain regions to visual and acoustic imagery--a spect study.

Regional cerebral blood flow (rCBF) was assessed by means of HMPAO-SPECT in two experimental groups. In a control condition both groups listened to abstract words, in the experimental condition they heard five names of objects. One group was advised to form visual images of the objects, the other group was advised to form acoustic images of the sounds made by these objects. Post-experimental questionnaires revealed that most of the subjects in the acoustic imagery condition had had visual images in addition to the acoustic ones. Both imagery conditions lead to approximately equal increases of rCBF in the left inferior occipital region and in the left thalamus. Flow increases in both hippocampal regions and the right inferior and superior temporal regions were larger in the acoustic than in the visual imagery condition. It is concluded that only the activation of left inferior occipital and left thalamic regions can be interpreted as being related to modality-specific visual aspects of imagery.

Auditory Perception↗
PubMed1991

Dopamine D2 receptor imaging with SPECT: studies in different neuropsychiatric disorders.

The purpose of the present study is to visualize and quantify dopamine D2 receptors in the living human brain using an 123I-labeled ligand and the single photon emission computerized tomography (SPECT) technique. S-(-)-Iodobenzamide [S-(-)-IBZM] has been shown to be a highly selective ligand with high affinity for D2 receptors in experimental studies. Five millicuries (185 MBq) of 123I-labeled S-(-)-IBZM was administered intravenously to 12 control subjects, 22 parkinsonian patients under L-Dopa therapy, 12 parkinsonian patients without L-Dopa, 10 unmedicated patients with Huntington's disease, and 12 patients under different neuroleptics. Data collection with a rotating double-head scintillation camera started 1 h after injection and lasted for 50 min. In a semiquantitative approach, a ratio was calculated between mean counts per pixel in the striatum and a region in the lateral frontal cortex, which was 1.74 +/- 0.10 in the control group. A marked reduction of this ratio was found in patients with Huntington's disease (1.38 +/- 0.12; p = 0.0001), no significant changes in untreated parkinsonian patients (1.67 +/- 0.14), but a reduction in L-Dopa-treated cases (1.59 +/- 0.13; p = 0.0014). A curvilinear relationship was found between total daily dose of neuroleptics and the reduction of this ratio. Estimated receptor blockade under full neuroleptic treatment was 75-80%. S-(-)-IBZM binding was reduced with increasing age (p less than 0.01). Specific binding was reduced markedly when the racemic mixture of IBZM was used, and no specific binding was seen with the R-(+)-isomer, demonstrating the stereoselectivity of IBZM binding.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Dynamic SPECT in two healthy volunteers to determine the optimal time for in vivo D2 dopamine receptor imaging with 123I-IBZM using the rotating gamma camera.

Dynamic SPECT was performed in two healthy male volunteers with a single slice brain dedicated camera (Strichman Medical Equipment 810, first study) and a rotating gamma camera (Siemens Dual Rota ZLC37, second study) to obtain information about the optimal imaging time for the dopamine D2 receptor specific ligand 123I-(S)-(-)-2-hydroxy-3-iodo-6-methoxy-N[(1-ethyl-2-pyrrolidinyl) methyl]-benzamide (123I-IBZM). Count rates in the basal ganglia and in several cerebral cortical regions were used to define specific and aspecific binding, respectively. On the basis of the first study, 90-150 min seemed the optimal time for rotating gamma camera 123I-IBZM-SPECT. On the basis of the second study the optimal period was considered to be 60-120 min. It is recommended to apply the same imaging time after injection in a protocol to all patients and volunteers as otherwise a comparison may not be reliable.

Adult↗
PubMed1991

Thalamic ischemia in transient global amnesia: a SPECT study.

We performed 99mTc-HMPAO SPECT in a patient during transient global amnesia and twice thereafter. SPECT during the attack showed a significant diminution of regional blood flow in the left thalamus and a less marked diminution in the right thalamus. Quantitative evaluation of global 99mTc-HMPAO uptake indicated a diffuse depression of cerebral blood flow. At follow-up to 40 days after the attack, global uptake and thalamic flow indices normalized, but there was a persistent reduction of left frontal flow values.

Amnesia↗
PubMed1991

Dopamine receptor classification, neuroanatomical distribution and in vivo imaging.

The classification of dopamine receptors and their neuroanatomical distribution is reviewed, including the newly discovered D3, D4 and D5 subtypes. In vivo imaging techniques and methods for quantification are briefly described and PET and SPECT studies of D2 receptors in schizophrenia, under neuroleptic treatment, in aging, Parkinson's disease, Huntington's disease, tardive dyskinesia and multisystem atrophies are reviewed and compared with our own results. A short description is given of imaging studies of D1 receptors.

Brain↗
PubMed1991

Technetium-99m-d,1-hexamethylpropyleneamine oxime (HMPAO) uptake and glutathione content in brain tumors.

Technetium-d, HMPAO SPECT was performed in 70 patients suffering from intracerebral tumors of various histologic types (glioma n = 30, meningioma n = 19, metastases n = 10, angioma n = 3, neuroma n = 2, lymphoma n = 2, neurocytoma n = 1, epidermoid n = 1, gliosis n = 1, cholesteatoma n = 1). Tumor classification was histologically verified in all subjects except in two cases with inoperable angiomas. SPECT was performed under resting state conditions with a dual-head rotating camera (SIEMENS ZLC 37) following intravenous injection of 18-25 mCi 99mTc-d, 1-HMPAO. Regional tracer deposit was expressed in terms of a cerebellar index (CBI). Significantly higher regional HMPAO uptake was found in meningiomas when compared with gliomas of different malignancy (ANOVA p less than 0.05). Within gliomas, regional uptake increased with malignancy (n.s.). In 23 patients, a total of 32 tumor specimens were obtained for histochemical analysis of glutathione (GSH) content using high-pressure liquid chromatography. A significant correlation (least square method, p less than 0.001) between CBIs and GSH values was found, supporting the hypothesis that GSH is the predominant factor for the conversion of the lipophilic complex to hydrophilic derivates.

Adult↗
PubMed1990

Comparison of [99mTc]HMPAO SPECT with [18F]fluoromethane PET in cerebrovascular disease.

Positron emission tomography (PET) of [18F]fluoromethane (FM) and single-photon emission tomography (SPECT) of [99mTc]hexamethylpropyleneamine oxime (HMPAO) were performed under identical conditions within 2 h in 22 patients suffering from cerebrovascular disease (8 ischemic infarction, 2 intracerebral hemorrhages, 7 transient ischemic attacks, and 5 multi-infarct syndrome). While gross pathological changes could be seen in the images of either procedure, focal abnormalities corresponding to transient ischemic deficits or to lesions in multi-infarct syndrome and areas of functional deactivation were sometimes missed on SPECT images. Overall, HMPAO SPECT images showed less contrast between high and low activity regions than the FM PET images, and differences between lesions and contralateral regions were less pronounced (6.4 vs 13.3% difference). Regional cerebral blood flow (rCBF) was calculated from FM PET studies in 14 large territorial regions and the pathological lesion, and the regional values relative to mean flow were compared to the relative HMPAO uptake in an identical set of regions defined on the SPECT images. Among individual patients, the Spearman rank-correlation coefficient between relative rCBF and HMPAO uptake varied between 0.48 and 0.89, with a mean of 0.70. While an underestimation of high flow with SPECT--which was demonstrated in a curvilinear relationship between all relative regional PET and SPECT values--could be corrected by linearization taking into account HMPAO efflux from the brain before metabolic trapping, correspondence of SPECT data with PET rCBF values was not improved since this procedure also increased the variance in high flow areas. In the cerebellum, however, a high HMPAO uptake in SPECT always overestimated CBF in relation to forebrain values; this finding might be due to high capillary density in the cerebellum. The differences observed between SPECT and PET data may be explained by technical and physical properties of the methods and by the incomplete first-pass extraction of HMPAO. Additionally, HMPAO or its metabolites may leak through a damaged blood-brain barrier (as observed in one infarct and in the surrounding of hemorrhages), impairing the contrast between lesion and normal tissue. The presented data indicate that the quantification of rCBF by HMPAO SPECT is limited.

Adult↗
PubMed1990

Sufentanil does not increase cerebral blood flow in healthy human volunteers.

The effect of sufentanil on human cerebral blood flow (CBF) was studied in seven unpremedicated, healthy volunteers 31 +/- 3.5 yr of age (mean +/- SD) and either sex. CBF (ml.100 g-1.min-1) was measured noninvasively with the 133Xe clearance technique and a scintillation camera before and after sufentanil 0.5 micrograms/kg administered intravenously. This technique provides values for global blood flow and for gray and white matter blood flow, and from 13 preselected regions in one hemisphere. After the administration of sufentanil, the volunteers were stimulated verbally in order to prevent their loss of consciousness and hypercarbia. Heart rate (HR), arterial pressure, oxyhemoglobin saturation, and end-tidal CO2 (ETCO2 were recorded during the measurements. Neither global CBF (46.1 +/- 1.6 control and 43 +/- 1.9 after sufentanil, mean +/- SEM) nor gray (76.5 +/- 3.2 and 70.9 +/- 6.1) or white (22.7 +/- 1.5 and 24.2 +/- 1.6) matter blood flow changed significantly after sufentanil administration. As well, no significant differences in HR (72 +/- 4 control and 79 +/- 4 beats per min after sufentanil) and ETCO2 (39.8 +/- 1.4 and 41.1 +/- 1.1 mmHg) were observed. It is concluded that sufentanil has no significant effect on CBF in healthy human volunteers.

Adult↗
PubMed1990

A contribution to classification of hallucinations.

Proceeding from the hypothesis that auditory hallucinations in psychotic patients have another biological basis than hallucinations provoked by hypnotic suggestion in healthy persons, we performed a symptom-comparative study by means of 99mTc-HMPAO single photon emission computed tomography. The results confirm the importance of pathogenesis in symptom-oriented psychiatric research.

Adult↗
PubMed1989

The cerebral localization of neuropsychological impairment in Alzheimer's disease: a SPECT study.

Twenty-three patients with a clinical diagnosis of Alzheimer's disease were examined with a set of neuropsychological tests and with 99mTc-hexamethyl-propyleneamineoxime (HMPAO) single photon emission computed tomography (SPECT). Correlations between test results and indices of regional HMPAO distribution were analysed by multidimensional scaling (MDS). Test results covaried positively with relative HMPAO uptake of frontal, inferior parietal and superior temporal regions but not, or in a negative way, with the remainder of the regions. When only positive correlations were analysed, MDS suggested two dimensions of organization: one was related to a dichotomy between frontal and temporo-parietal regions. The relationship of test results to this dimension was largely consistent with common neuropsychological knowledge. A second, less stringent dimension of organization opposed right and left hemisphere regions. The ordering of test results with respect to this dimension was only partly consistent with what is known about the lateralization of neuropsychological deficits from the study of localized brain lesions. The possibility is considered that these inconsistencies may reflect the effect of disproportionally severe involvement of extended cortical systems which modulates the sequels of localized brain damage.

Aged↗
PubMed1989

Regional cerebral blood flow patterns in visual imagery.

Regional cerebral blood flow patterns were investigated by means of single photon emission computerized tomography in subjects who solved cognitive tasks which either did or did not require the use of visual imagery. In a first experiment judging the correctness of visual imagery sentences like "a grapefruit is bigger than an orange" led to increases of regional activity in inferior temporal and in the left inferior-occipital region when compared to blood flow patterns elicited by judgements about low imagery sentences or by responding differentially to "yes" and "no". Motor imagery sentences did not cause such an increase. In a second experiment a condition in which visual images were used for counting the corners of letters was compared to a condition in which subjects internally rehearsed the alphabet. The only difference concerned the inferior frontal regions which showed higher activity in rehearsing the alphabet. However, activity in inferior temporal and inferior occipital regions showed a positive correlation to the self-rated vividness of the visual images in the corner counting condition. The results of both experiments yield converging evidence that visual imagery is selectively related to activity of inferior-temporal and occipital regions. They thus support the hypothesis that the cerebral correlate of visual imagery is different from that of non-imaginal thinking.

Adult↗
PubMed1989

Cerebral correlates of imagining colours, faces and a map--I. SPECT of regional cerebral blood flow.

The distribution of regional cerebral blood flow (rCBF) was assessed by single photon emission computerized tomography (SPECT) in subjects during a resting state and during imagining either colours or faces or a route on a map. Twelve out of 30 subjects reported the spontaneous occurrence of mental visual images during the resting state. In these subjects flow in both orbitofrontal regions was higher than in those subjects who had not experienced spontaneous imagery. Voluntary imagery led to an increase of regional flow indices in basal temporal regions of both hemispheres and to a rightwards shift of global hemispheric asymmetry. The local changes were distinctly more marked with faces than with any of the other two stimuli. Imagining faces was also the only condition that led to an increase of activity in the left inferior occipital region which has been suggested by previous studies as being a crucial area for visual imagery. It is concluded that the observed differences of rCBF patterns between imagery conditions are related to the amount of information conveyed by the mental image. In contrast to the results of a companion study on DC-shifts accompanying imagery there was no effect of the visual versus spatial character of the images.

Adult↗
PubMed1989

Diffuse cerebrospinal gliomatosis presenting as motor neuron disease for two years.

A patient with symptoms and signs of motor neuron disease for 2 years finally developed sensory disturbances and increased intracranial pressure. MRI and CT showed enlargement of the right side of the cerebellum, the brainstem and parts of the cerebral hemisphere with focal hyperperfusion demonstrated by SPECT. Necropsy revealed a diffuse cerebrospinal gliomatosis with loss of spinal motor neurons in tumour infiltration of the anterior horns. This type of spinal cord involvement is considered responsible for the unusual clinical presentation of the neoplasm.

Adult↗
PubMed1989

Quantification of regional cerebral blood flow with IMP-SPECT. Reproducibility and clinical relevance of flow values.

Single-photon emission computed tomography with N-isopropyl[123I]-p-iodoamphetamine (IMP-SPECT) was performed in 14 normal volunteers (seven men and seven women aged 25.1 +/- 5.3 years) and 29 patients with cerebrovascular disease (18 men and 11 women aged 54.1 +/- 13.7 years). The fluid microsphere model was used to estimate cerebral blood flow (CBF). Normal subjects were scanned twice, 1 week apart, to determine the reproducibility of the CBF estimates. Hemispheric blood flow (hCBF) was calculated as the mean of regional cerebral blood flow (rCBF) values in 16 gray matter regions per hemisphere. In normal subjects mean hCBF was 68 ml/100 g/min. The highest rCBF was found in the occipital cortex, followed by the frontal, temporal, and parietal cortexes. CBF values were reproducible (p less than 0.001 except the right thalamic region, where p less than 0.01). Intraindividual variation ranged between 0.3% and 15%. Women exhibited significantly higher (16%, p less than 0.02) CBF than men. Patients were subdivided into groups with reversible (n = 19) and persistent (n = 10) symptoms. Significant hCBF differences between the affected and the contralateral hemispheres were recorded only in the group with reversible symptoms (p less than 0.005), whereas the group with persistent symptoms showed a significant bilateral decrease of hCBF compared with normal subjects and patients with reversible symptoms. Focal CBF was significantly lower in patients with completed stroke than in patients with transient symptoms (p less than 0.001). Our results indicate that IMP-SPECT can be used for the routine estimation of CBF in normal and pathologic states.

Aged↗
PubMed1988

DC-potential shifts and regional cerebral blood flow reveal frontal cortex involvement in human visuomotor learning.

In the present study, two different physiological parameters were measured to describe brain activity related to visuomotor learning: performance-related DC-potential shifts and regional cerebral blood flow (rCBF) by Tc-99m HMPAO brain SPECT (Single Photon Emission Computerized Tomography). Visuomotor learning was required in a conflicting situation: a visual target moved on a screen and had to be tracked by moving the right hand in an inverted fashion (IT), e.g. movements of the target to the right side required hand movement to the left and vice versa. Compared to a normal, non-inverted control task (T), IT required the development of a novel motor program and the prevention of returning to routine direct pursuit. These additional demands in IT caused a relative hyperperfusion in regions including the middle frontal gyri, frontomedial cortex (including the supplementary motor area, SMA), right basal ganglia (caudate-putamen) and left cerebellum. Correlations of rCBF values between the middle frontal gyrus and basal ganglia may indicate a functional relation between these two brain structures. Visuomotor performance was accompanied by slow negative DC-potential shifts. In frontal and to a lesser degree in central recordings, amplitudes of DC-negativity were larger in IT than they were in T. This additional frontal negativity covaried with the success of learning. Results substantiate, now using a dual approach, previous suggestions that the frontal lobe plays an important role in visuomotor learning.

Adolescent↗
PubMed1988

Single photon emission computerized tomography during and between seizures.

In three patients, patterns of brain activity were measured by 99mTc-hexamethyl-propyleneamineoxime (99mTc-HM-PAO) brain SPECT (single photon emission computerized tomography) in ictal and interictal states. Increased relative blood flow indicated the focus of partial seizures, its spreading to adjacent cortical regions and to distant brain structures via neuronal pathways. Ictal patterns of regional cerebral blood flow (rCBF) were in agreement with clinical symptomatology. Successive SPECT studies were performed after 3-7 days in the absence of electroencephalographic and clinical signs of seizures but still revealed increased relative blood flow in the focus of the seizures. SPECT studies, performed 2-6 weeks after the last clinically observable seizures, demonstrated the transition from increased to decreased relative blood flow in the focus of the seizures. In one patient, the EEG was complementary to and corresponded with the rCBF patterns in the ictal state. However, the dynamics of interictal changes could only be assessed by brain SPECT.

Adult↗
PubMed1988

Hexa-methyl-propylene-amine-oxime (HMPAO) single photon emission computed tomography (SPECT) in epilepsy.

Twenty-eight normal volunteers and 74 seizure patients were investigated with hexa-methyl-propylene-amine-oxime (HMPAO) brain single photon emission computed tomography (SPECT). Fifty-four patients suffered from partial seizures and 20 patients had generalized seizures. Indices describing regional tracer distribution (RIs) were calculated in all investigated subjects. Regions whose RI exceeded the mean normal RI +/- 3 SD were defined as abnormally perfused. In normals a significant interhemispheric asymmetry of HMPAO deposition was found, with higher RI values in the right frontal, parietal, temporal and occipital regions. In 59.3% of partial seizure patients abnormal RIs were found. Low RIs were detected predominantly in the frontal and temporal cortex, while elevated RIs were observed predominantly in the anterior basal ganglia. Only in 20% of the cases with generalized seizures, abnormal RIs were found. In one patient an ictal and 3 follow-up SPECT studies were obtained. Here SPECT results indicated transient rCBF changes between the ictal and seizure free state. EEG and SPECT foci were ipsilaterally located in 69.2% of the partial seizure cases. The results indicate that HMPAO brain SPECT is valuable for the detection of rCBF abnormalities in seizure patients and that patients with partial seizures have mostly several abnormally perfused areas in their brains.

Adult↗